U.S. patent application number 11/963276 was filed with the patent office on 2008-06-26 for image sensor and method for manufacturing the same.
Invention is credited to Young Je Yun.
Application Number | 20080150059 11/963276 |
Document ID | / |
Family ID | 39541620 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080150059 |
Kind Code |
A1 |
Yun; Young Je |
June 26, 2008 |
Image Sensor and Method for Manufacturing the Same
Abstract
An image sensor and a manufacturing method thereof are provided.
An insulating layer structure can be formed on a photodiode region
and can include a trench. A color filter structure can be formed on
the insulating layer structure having color filters corresponding
to photodiodes in the photodiode region. The upper surfaces of the
color filters can be about even with each other.
Inventors: |
Yun; Young Je; (Ansan-si,
KR) |
Correspondence
Address: |
SALIWANCHIK LLOYD & SALIWANCHIK;A PROFESSIONAL ASSOCIATION
PO BOX 142950
GAINESVILLE
FL
32614-2950
US
|
Family ID: |
39541620 |
Appl. No.: |
11/963276 |
Filed: |
December 21, 2007 |
Current U.S.
Class: |
257/432 ;
257/E31.127; 438/70 |
Current CPC
Class: |
H01L 27/14621
20130101 |
Class at
Publication: |
257/432 ; 438/70;
257/E31.127 |
International
Class: |
H01L 31/18 20060101
H01L031/18; H01L 31/0232 20060101 H01L031/0232 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2006 |
KR |
10-2006-0132348 |
Claims
1. An image sensor, comprising: a semiconductor substrate; a first
photodiode in a first pixel area, a second photodiode in a second
pixel area, and a third photodiode in a third pixel area on the
semiconductor substrate; an insulating layer structure on the
semiconductor substrate, wherein the insulating layer structure
comprises a trench over the third pixel area; and a color filter
structure on the insulating layer structure, the color filter
structure comprising a first color filter corresponding to the
first pixel area, a second color filter corresponding to the second
pixel area, and a third color filter corresponding to the third
pixel area; wherein the third color filter is provided on the
trench.
2. The image sensor according to claim 1, further comprising a
microlens on the color filter structure.
3. The image sensor according to claim 1, wherein the trench has a
thickness of about 400 nm.
4. The image sensor according to claim 1, wherein the third color
filter is thicker than the first color filter; and wherein an upper
surface of the first color filter is about even with an upper
surface of the second color filter and an upper surface of the
third color filter.
5. The image sensor according to claim 1, wherein a thickness of
the first color filter is approximately equal to a thickness of the
second color filter.
6. The image sensor according to claim 1, wherein the insulating
layer structure further comprises: a second trench over the second
pixel area, wherein the second color filter is provided on the
second trench.
7. The image sensor according to claim 6, wherein the second color
filter is thicker than the first color filter, and wherein the
third color filter is thicker than the second color filter.
8. The image sensor according to claim 7, wherein an upper surface
of the first color filter is about even with an upper surface of
the second color filter and an upper surface of the third color
filter.
9. The image sensor according to claim 1, wherein the first color
filter is a blue color filter, the second color filter is a green
color filter, and the third color filter is a red color filter.
10. A method for manufacturing an image sensor, comprising: forming
photodiode regions including a first photodiode, a second
photodiode, and a third photodiode on a semiconductor substrate;
forming an insulating layer structure including a trench formed
over the third photodiode; forming a first color filter over the
first photodiode on an upper surface of the insulating layer
structure; forming a second color filter over the second photodiode
on the upper surface of the insulating layer structure; and forming
a third color filter over the third photodiode in the trench of the
insulating layer structure.
11. The method according to claim 10, wherein forming the
insulating layer structure comprises: depositing a photoresist
material on an insulating layer; exposing and developing the
photoresist film to form a photoresist pattern; and etching the
insulating layer using the photoresist pattern as an etch mask to
form the trench; wherein an exposure mask used to expose the
photoresist film is identical to an exposure mask used to expose a
material used to form the third color filter.
12. The method according to claim 11, wherein the photoresist film
is a positive type photoresist material, and the material used to
form the third color filter material is a negative type photoresist
material.
13. The method according to claim 10, wherein forming the
insulating layer structure comprises etching an insulating layer
through reactive ion etching to form the trench.
14. The method according to claim 10, wherein the trench has a
depth of about 400 nm.
15. The method according to claim 10, wherein a thickness of the
second color filter is approximately equal to a thickness of the
first color filter; and wherein the third color filter is thicker
than the first color filter; and wherein an upper surface of the
first color filter is about even with an upper surface of the
second color filter and an upper surface of the third color
filter.
16. The method according to claim 10, wherein the insulating layer
structure further comprises: a second trench over the second
photodiode, wherein the second color filter is formed on the second
trench.
17. The method according to claim 16, wherein the second color
filter is thicker than the first color filter, and wherein the
third color filter is thicker than the second color filter.
18. The method according to claim 10, wherein an upper surface of
the first color filter is about even with an upper surface of the
second color filter and an upper surface of the third color
filter.
19. The method according to claim 10, wherein the first color
filter is a blue color filter, the second color filter is a green
color filter, and the third color filter is a red color filter.
20. The method according to claim 11, further comprising forming a
microlens on each of the first color filter, the second color
filter, and the third color filter.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit under 35 U.S.C.
.sctn.119 of Korean Patent Application No. 10-2006-0132348, filed
Dec. 22, 2006, which is hereby incorporated by reference in its
entirety.
BACKGROUND
[0002] Image sensors are semiconductor devices that convert optical
images into electrical signals and can be classified as charge
coupled devices (CCD) or complimentary metal oxide semiconductor
(CMOS) image sensors.
[0003] In a typical related art method for manufacturing an image
sensor, transistors and a photodiode electrically connected to the
transistors are formed on a semiconductor substrate. An insulating
layer structure and an interconnection are formed on the
transistors and the photodiode, and red, green, and blue color
filters are formed on the insulating layer structure.
[0004] According to typical related art methods for manufacturing
an image sensor, because the color filters have different
thicknesses, a photoresist material is coated on an upper surface
of the color filters to form a planar layer. Then, another
photoresist film is coated on the upper surface of the planar
layer, and a reflow process is performed to form a microlens to
provide light concentrated on the photodiode. However, the planar
layer covering the color filters can cause light loss. In other
words, as the thickness of the planar layer increases, the
sensitivity of an optical signal is degraded, such that the
performance of the image sensor can also be degraded.
[0005] In addition, according to related art methods for
manufacturing an image sensor, the planar layer can inhibit the
microlens from being precisely focused on a pixel area.
Accordingly, in order to compensate for a focus distance due to the
thickness of the planar layer, the microlens is often formed to be
thinner. However, this can reduce a process margin of the image
sensor.
[0006] Furthermore, a coating strip pattern can be formed in the
process of forming the microlens due to the difference in thickness
between a pixel area formed with both the color filters and the
planar layer and a scribe line having no color filters or planar
layer.
[0007] Thus, there exists a need in the art for an improved image
sensor and manufacturing method thereof.
BRIEF SUMMARY
[0008] Embodiments of the present invention provide an image sensor
and a manufacturing thereof capable of forming color filters having
upper surfaces that are even with each other.
[0009] In an embodiment, an image sensor can include a photodiode
region, an insulating layer structure including a trench on the
photodiode region, and a color filter structure on the insulating
layer structure. The color filter structure can include a first
color filter, a second color filter, and a third color filter. The
third color filter can be thicker than the first color filter, and
the upper surface of the first color filter can be about even with
the upper surfaces of the second color filter and the third color
filter.
[0010] In an embodiment, a method for manufacturing an image sensor
can include: forming a photodiode region on a semiconductor
substrate; forming an insulating layer structure including a trench
on the photodiode region; forming a first color filter by coating
and patterning a first color filter material on the upper surface
of the insulating layer structure; forming a second color filter by
coating and patterning a second color filter material on the upper
surface of the insulating layer structure; and forming a third
color filter by coating and patterning a third color filter
material on the upper surface of the insulating layer structure,
wherein the third color filter is thicker than the first color
filter, and the upper surface of the first color filter is about
even with the upper surfaces of the second color filter and the
third color filter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-sectional view showing an image sensor
according to an embodiment of the present invention.
[0012] FIG. 2 is a plan view showing a photodiode region shown in
FIG. 1.
[0013] FIGS. 3 to 8 are cross-sectional views showing a method for
manufacturing an image sensor according to an embodiment of the
present invention.
DETAILED DESCRIPTION
[0014] When the terms "on" or "over" are used herein, when
referring to layers, regions, patterns, or structures, it is
understood that the layer, region, pattern or structure can be
directly on another layer or structure, or intervening layers,
regions, patterns, or structures may also be present. When the
terms "under" or "below" are used herein, when referring to layers,
regions, patterns, or structures, it is understood that the layer,
region, pattern or structure can be directly under the other layer
or structure, or intervening layers, regions, patterns, or
structures may also be present.
[0015] FIG. 1 shows an image sensor 300 according to an embodiment
of the present invention, and FIG. 2 is a plan view showing a
photodiode region shown in FIG. 1.
[0016] Referring to FIG. 1, the image sensor 300 according to an
embodiment can include photodiode pixel regions 100, an insulating
layer structure 150, a color filter structure 200, and microlenses
250. The photodiode pixel regions 100 can be formed in a pixel area
of a semiconductor substrate 10 to generate an electrical signal by
incident light. The photodiode pixel regions 100 can include any
suitable number of photodiodes. In an embodiment, the photodiode
pixel regions 100 can include a first pixel region 102, a second
pixel region 104, and a third pixel region 106.
[0017] Referring to FIG. 2, each photodiode pixel region 20 of the
photodiode pixel regions 100 (for example, the first pixel region
102, the second pixel region 104, and the third pixel region 106)
can include a photodiode PD which can detect light, a transfer
transistor Tx, a reset transistor Rx, a select transistor Sx, and
an access transistor Ax. A drain of the transfer transistor Tx can
serve as a floating diffusion FD region.
[0018] Referring again to FIG. 1, the insulating layer structure
150 can include an insulating layer 152 to insulate multi-layer
interconnections (not shown) from each other by covering an upper
portion of the semiconductor substrate 10 including the photodiode
pixel regions (for example, the first pixel region 102, the second
pixel region 104, and the third pixel region 106) and a trench 154
formed with a predetermined depth in an upper portion of the
insulating layer 152 corresponding to a photodiode (for example,
the third pixel region 106). The depth of the trench 154 can be,
for example, about 300 nm to about 500 nm.
[0019] The color filter structure 200 can be formed on the upper
surface of the insulating layer structure 150 to transmit light of
specific colors. The color filter structure 200 can include a blue
color filter 202, a green color filter 204, and a red color filter
206. In an embodiment, the blue color filter 202 can be formed on
the upper surface of the insulating layer 152 corresponding to the
first pixel region 102, the green color filter 204 can be formed on
the upper surface of the insulating layer 152 corresponding to the
second pixel region 104, and the red color filter 206 can be formed
in the trench 154 of the insulating layer structure 150
corresponding to the third pixel region 106.
[0020] In an embodiment, the thickness of the blue color filter 202
can be approximately equal to the thickness of the green color
filter 204 while the red color filter 206 can be thicker than the
blue color filter 202 and the green color filter 204. The thickness
of the red color filter 206 can be larger than that of the blue
color filter 202 and the green color filter 204 by the depth of the
trench 154. Thus, although the red color filter 206 is thicker than
the blue color filter 202 and the green color filter 204, the upper
surface of the red color filter 206 can be approximately even with
the upper surface of the blue color filter 202 and the upper
surface of the green color filter.
[0021] In an embodiment, in order to inhibit colors from being
mixed with each other, which can sometimes occur when the green
color filter 204 transmits not only the light having the green
wavelength band but also the light having wavelengths similar to
the blue wavelength, the green color filter 204 can be slightly
thicker than the blue color filter 202. In order to form the color
filter structure 200 with a uniform upper surface while forming the
green color filter 204 slightly thicker than the blue color filter
202, a second trench having a depth corresponding to the difference
in thickness between the green color filter 204 and the blue color
filter 202 can be formed in a portion of the insulating layer 152
corresponding to the green color filter 204.
[0022] The microlenses 250 condense light to the photodiode pixel
regions 100, and can be formed in a partially spherical shape on
the upper surface of the color filter structure 200.
[0023] According to embodiments of the present invention the upper
surface of the color filter structure 200 can be uniform and the
microlens 250 can be formed directly on the color filter structure
200 without forming a planar layer.
[0024] Therefore, since a planar layer is not present between the
color filter structure 200 and the microlens 250, light loss can be
reduced while light is being transferred to the photodiode pixel
region 100. Also, the microlens 250 can be focused more precisely
on the photodiode PD, such that the microlens 250 can be easily
formed. In addition, since a step difference between a scribe line
and a pixel area formed with photodiode regions is only slightly
generated, the occurrence of coating stripes can be inhibited
during the coating of a photoresist material used to form the
microlens 250.
[0025] In addition, color mixture phenomenon can be inhibited since
the blue color filter 202, the green color filter 204, and the red
color filter 206 can have varying thicknesses while the upper
surface of the color filter structure 200 can be approximately
uniform.
[0026] FIGS. 3 to 8 show a method for manufacturing an image sensor
300 according to an embodiment of the present invention.
[0027] FIG. 3 is a cross-sectional view showing photodiode pixel
regions 100 of an image sensor according to an embodiment of the
present invention.
[0028] Referring to FIG. 3, in the photodiode pixel regions 100
including the first pixel region 102, the second pixel region 104,
and the third pixel region 106) can be formed on the semiconductor
substrate 10. Although FIG. 3 shows the first pixel region 102, the
second pixel region 104, and the third pixel region 106, the
photodiode pixel regions 100 can include any suitable number of
pixel regions as desired to provide a particular resolution.
[0029] Referring to FIG. 4A, after forming the photodiode pixel
regions 100 on the semiconductor substrate 10, an insulating layer
152 can be formed on the semiconductor substrate 10 over the pixel
regions 100.
[0030] Then, a photoresist film 160 can be coated on the upper
surface of the insulating layer 152. The photoresist film 160 can
include, for example, a positive type photoresist material in which
cross-links are disconnected in portions exposed to the light.
[0031] Referring to FIG. 4B, after the photoresist film 160 is
coated on the insulating layer, the photoresist film 160 can be
exposed by using an exposure mask such that a portion of the
photoresist film 160 corresponding to the third pixel region 106 is
exposed to light. Then, the photoresist film 160 can be patterned
into a first photoresist pattern 160a by etching the photoresist
film 160. When the photoresist film 160 is etched, only a portion
of the photoresist film 160, in which the cross-link is
disconnected through the reaction with light, that is, only the
portion of the photoresist film 160 corresponding to the third
pixel region 106 is removed.
[0032] Then, the insulating layer 152 can be etched through
reactive ion etching (RIE) by using the first photoresist pattern
160a as an etch mask. By etching a portion of the insulating layer
152 corresponding to the third pixel region 106, a trench 154
having a predetermined depth can be formed. For example, the depth
of the trench 154 can be about 300 nm to about 500 nm.
[0033] Referring to FIGS. 5A and 5B, after forming the insulating
layer structure 150, the blue color filter 202 can be formed on the
insulating layer structure 150.
[0034] In order to form the blue color filter 202, a blue color
filter material can be coated over the entire surface of the
insulating layer structure 150, thereby forming a blue color filter
layer 202a. The blue color filter material can include, for
example, a blue pigment and/or a dye and a photoresist material. In
an embodiment, the photoresist material can be a negative type
photoresist material, in which cross-links are formed in portions
exposed to light.
[0035] Then, the blue color filter layer 202a can be patterned
through a photo process including a lithography process and a
development process to form the blue color filter 202 on the
insulating layer structure 150 corresponding to the first pixel
region 102.
[0036] Referring to FIGS. 6A and 6B, the green color filter 204 can
be formed on the insulating layer structure 150.
[0037] In order to form the green color filter 204, a green color
filter material can be coated over the entire surface of the
insulating layer structure 150, thereby forming a green color
filter layer 204a. The green color filter material can include, for
example, a green pigment and/or a dye and a photoresist material.
In an embodiment, the photoresist material can be a negative type
photoresist material in which cross-links are formed at portions
exposed to light.
[0038] Then, the green color filter layer 204a can be patterned
through a photo process including a lithography process and a
development process to form the green color filter 204 on the
insulating layer structure 150 corresponding to the second pixel
region 104.
[0039] In one embodiment, the thickness of the green color filter
204 is approximately equal to the thickness of the blue color
filter 202.
[0040] Referring to FIGS. 7A and 7B, the red color filter 206 can
be formed on the insulating layer structure 150.
[0041] In order to form the red color filter 206, a red color
filter material can be coated over the entire surface of the
insulating layer structure 150, thereby forming a red color filter
layer 206a. The red color filter material can include, for example,
a red pigment and/or a dye and a photoresist material. In an
embodiment, the photoresist material can be a negative type
photoresist material, in which cross-links are formed at portions
exposed to light.
[0042] Then, the red color filter layer 206a can be exposed by
using an exposure mask processed such that a portion of the red
color filter layer 206a over the trench 154 can be exposed to
light. The red color filter layer 206a can be patterned through a
process of developing the red color filter layer 206a to form the
red color filter 206 in the trench 154. The red color filter 206
can be formed thicker than the blue color filter 202 and the green
color filter 204.
[0043] The exposure process of the red color filter layer 206a can
be performed by using the same exposure mask as that used to expose
the photoresist film 160 coated on the upper surface of the
insulating layer 152 in order to form the trench 154. If the red
color filter layer 206a is patterned through the development
process, only a portion of the red color filter layer 206a which
has reacted with light to form a cross-link remains instead of
being removed. That is, only a portion of the red color filter
layer 206a over the trench 154 remains so that the red color filter
206 can be formed.
[0044] In an embodiment, the thickness of the red color filter 206
can be thicker than that of the blue color filter 202 and the green
color filter 204 by the depth of the trench 154. Thus, referring to
FIG. 7B, although the red color filter 206 can be thicker than the
blue color filter 202 and the green color filter 204, the upper
surfaces of the blue color filter 202, the green color filter 204,
and the red color filter 206 are approximately even with each other
due to the trench 154.
[0045] Then, referring to FIG. 8, after forming the red color
filter 206 in the trench 154, a photoresist material can be
directly coated on the upper surface of the blue color filter 202,
the green color filter 204, and the red color filter 206, and then
the resultant structure can be subject to a reflow process to form
the microlens 250. Thus, no planar layer is needed to be formed on
the upper surface of the blue color filter 202, the green color
filter 204, and the red color filter 206.
[0046] According to an embodiment of the present invention, the
thickness of the blue color filter 202 can be approximately equal
to the thickness of the green color filter 204, and the red color
filter 206 can be thicker than the blue color filter 202 and the
green color filter 204 by the depth of the trench 154. Thus, the
upper surfaces of the blue color filter 202, the green color filter
204, and the red color filter 206 can be about even with each
other.
[0047] In another embodiment, in order to inhibit colors from being
mixed with each other, which can sometimes occur when the green
color filter 204 transmits light having wavelengths similar to the
blue wavelength band, the green color filter 204 can be slightly
thicker than the blue color filter 202. In order to form the color
filter stricture 200 having a uniform upper surface while forming
the green color filter 204 slightly thicker than the blue color
filter 202, a trench having a depth corresponding to the difference
in thickness between the green color filter 204 and the blue color
filter 202 can be formed in a portion of the insulating layer 152
corresponding to the second pixel region 104. The trench 154 for
the red color filter 204 can still be formed in a portion of the
insulating layer 152 corresponding to the third pixel region 104.
In such an embodiment, a second photoresist film can be used before
or after patterning and developing the first photoresist film 160
and etching the insulating layer 152 to form the trench 154.
[0048] In embodiments of the present invention, the upper surface
of the color filter structure can be uniform, so that the microlens
can be directly formed on the top surface of the color filter
structure without forming a planar layer. Accordingly, the
manufacturing process of the image sensor can be simplified.
[0049] In addition, since a planar layer is not present between the
color filter structure and the microlens, light loss can be reduced
while light is being transferred to the photodiode region, and the
microlens can be used to focus light on the photodiode more
precisely. This can improve the performance of the image sensor and
allow the microlens to be easily formed.
[0050] Furthermore, since a step difference between the scribe line
and the pixel area formed with the photodiode regions can be thin,
the occurrence of coating stripes can be minimized when the
photoresist material is coated while forming the microlens.
Accordingly, the occurrence of bending and discolor phenomena can
be reduced.
[0051] Moreover, in an embodiment since the upper surface of the
color filter structure is uniform, and the red and green color
filters are thicker than the blue color filter, the color mixture
phenomenon can be inhibited from occurring.
[0052] Any reference in this specification to "one embodiment," "an
embodiment," "example embodiment," etc., means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
invention. The appearances of such phrases in various places in the
specification are not necessarily all referring to the same
embodiment. Further, when a particular feature, structure, or
characteristic is described in connection with any embodiment, it
is submitted that it is within the purview of one skilled in the
art to effect such feature, structure, or characteristic in
connection with other ones of the embodiments.
[0053] Although embodiments have been described with reference to a
number of illustrative embodiments thereof, it should be understood
that numerous other modifications and embodiments can be devised by
those skilled in the art that will fall within the spirit and scope
of the principles of this disclosure. More particularly, various
variations and modifications are possible in the component parts
and/or arrangements of the subject combination arrangement within
the scope of the disclosure, the drawings and the appended claims.
In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to
those skilled in the art.
* * * * *